Energy storage system and vehicle with the same

Abstract

Energy storage system (18), comprising: a heat dissipation device, in particular an energy storage cell pack (20) including a first cell (20-1) and a second cell (20-2) arranged adjacent to the first cell (20-1), each of the first and second cells (20-1, 20-2) being configured to generate and store electrical energy through electrochemical reactions that generate heat energy; a heat sink (22) configured to absorb and dissipate the thermal energy released by the first and second cells (20-1, 20-2); and a first thermal interface element (24) disposed between the first cell and the second cell (20-1, 20-2), comprising a first thermally conductive, curable polymer foam pad (26) and configured to: maintain uniform contact with the first cell and the second cell (20-1, 20-2) during alternating expansion of the first and second cells (20-1, 20-2) during charging and contraction of the first and second cells (20-1, 20-2) during discharging; and absorb the heat energy released by a heat dissipation device formed by the first cell (20-1) and the second cell (20-2) and conduct the heat energy to the heat sink (22), wherein a further thermal interface element (34) arranged between the heat sink (22) and the heat dissipation device and comprising: a thermally conductive, curable further polymer foam pad (36) configured to maintain uniform contact with each of the heat sink (22) and the heat dissipator, absorb thermal energy released by the heat dissipator, and conduct the released thermal energy to the heat sink (22); characterized in that the further polymer foam pad (36) has a matrix structure (28) which includes at least one of an anisotropic thermally conductive filler material and an isotropic thermally conductive filler material and is characterized by a foam density below 0.5 g / cm 3 is marked, and that the further polymer foam pad (36) is electrically conductive and the further thermal interface element (34) additionally includes an electrical insulating layer (40) or the further polymer foam pad (36) is electrically non-conductive and is characterized by the absence of an electrical insulating element.

Description

[0001] The invention relates to an energy storage system according to the preamble of claim 1 and a vehicle having such an energy storage system, wherein the energy storage system comprises a hardening, lightweight, thermally conductive interface between a thermal energy source and adjacent structures.

[0002] Various electrical and electronic devices, such as energy storage cells, control modules, electric motors, computers, etc., release waste heat as a by-product of their main operation.

[0003] Energy storage cells, such as batteries and accumulators, can be broadly classified into primary and secondary energy storage units. Primary energy storage cells, such as disposable batteries, are designed to be used until they are discharged, after which they are simply replaced with one or more new energy storage cells. Secondary energy storage cells, such as rechargeable batteries, are capable of repeated recharging and reuse and therefore offer economic, environmental, and ease-of-use benefits compared to disposable energy storage units. Both primary and secondary energy storage cells can be interconnected and organized into energy storage cell packs to deliver the desired voltage, capacity, or power density.

[0004] DE 10 2017 100 030 A1 describes methods and devices for providing an even distribution of the waste heat in a battery pack, comprising a battery pack, a cold plate, a coolant reservoir, a support structure between the battery pack and the coolant reservoir, and a deformable thermally conductive paste for filling the space between cells of the battery pack and the coolant reservoir to provide thermal contact between the cells and the coolant reservoir to distribute the waste heat.

[0005] WO 2011 / 084 804 A2 deals with an energy supply system comprising an energy storage device including a housing. The energy supply system also includes a sheet material in contact with the housing. The sheet material includes a foam layer. The sheet material has a thermal conductivity of at least 0.1 W / mK and a thickness of at least 0.3 mm.

[0006] Secondary cells, such as lithium-ion batteries, tend to be more susceptible to thermal short circuits, or uncontrolled internal temperature rises, than primary cells. Specifically, thermal short circuits occur when the internal reaction rate increases until more heat is generated than can be dissipated, leading to a further increase in both the reaction rate and heat generation. Eventually, the amount of heat generated may be large enough to result in a loss of the cell's usefulness as well as damage to materials near the cell. Thermal short circuits in secondary energy storage cells can be triggered by a short circuit within the cell, misuse of the cell, physical abuse, manufacturing defects, or exposure to extreme external temperatures.

[0007] During a thermal short event, a large amount of heat energy is rapidly released, heating the entire cell to a temperature of 900°C or more. Due to the elevated temperature of the cell undergoing a thermal short, the temperature of adjacent cells within the battery pack typically also increases. If the temperature of adjacent cells is allowed to rise unchecked, such cells may also enter a thermal short condition—leading to a cascading effect in which the initiation of the thermal short within a single cell spreads throughout the entire storage cell pack. As a result, performance from the cell pack may be interrupted, while a system using the cell pack may suffer collateral damage due to the extent of the thermal short and the associated release of heat energy.

[0008] An energy storage system according to the invention comprises a heat dissipation device, in particular an energy storage cell pack including a first cell and a second cell arranged adjacent to the first cell, each of the first and second cells being configured to generate and store electrical energy through electrochemical reactions that generate thermal energy; a heat sink configured to absorb and dissipate the thermal energy released by the first and second cells; and a first thermal interface element arranged between the first cell and the second cell, which has a first thermally conductive, curable polymer foam pad and is configuredto maintain uniform contact with the first cell and the second cell during alternating expansion of the first and second cells upon charging and contraction of the first and second cells upon discharging; and to absorb the thermal energy released by a heat dissipation device formed by the first cell and the second cell and conduct the thermal energy to the heat sink. A further thermal interface element of the energy storage system is disposed between the heat sink and a heat dissipation device and includes a thermal interface element. The further thermal interface element comprises a thermally conductive, curable further polymer foam pad configured to maintain uniform contact with both the heat sink and the heat dissipation device. The further thermal interface element is additionally configuredto absorb the heat energy released by the heat dissipation device and conduct the released heat energy to the heat sink. The further polymer foam padding has a matrix structure that includes at least one anisotropic and isotropic thermally conductive filler material and is characterized by a foam density below 0.5 g / cm³. 3 characterized in that the further polymer foam pad is electrically conductive and the further thermal interface element additionally includes an electrical insulating layer, or the further polymer foam pad is electrically non-conductive and is characterized by the absence of an electrical insulating element.

[0009] The thermal interface element may include an anisotropic, thermally conductive layer configured to conduct the thermal energy released by the heat dissipation device to the heat sink.

[0010] The thermally conductive layer may be anisotropic and include at least one of boron nitride, graphite, and graphene.

[0011] The thermally conductive layer may be isotropic and include at least one of aluminum nitride, silicon carbide, aluminum oxide, zinc oxide, metal powders, and synthetic diamond.

[0012] The polymer foam pad may include a heat-resistant, thermosetting polymer comprising at least one of silicone, acrylic, polyurethane, polyvinyl ester, polycycloolefin, polyolefin, and polystyrene.

[0013] The matrix structure of the polymer foam cushion can comprise an open-cell or closed-cell foam construction. Furthermore, the closed-cell foam construction can include a foaming agent configured as microcapsules.

[0014] The polymer foam pad is electrically conductive, and the thermal interface element also has an electrically insulating layer.

[0015] The electrical insulating layer may be configured as a polyethylene terephthalate (PET) film.

[0016] Alternatively, the polymer foam pad is electrically non-conductive and is characterized by the absence of an electrical insulating element.

[0017] The first thermal interface element may include an anisotropic, thermally conductive layer disposed between the first polymer foam pad and at least one of the first cell and the second cell. In such an embodiment, the thermally conductive layer is configured to conduct the thermal energy released by the at least one of the first cell and the second cell to the heat sink. The anisotropic, thermally conductive layer may be a coating applied directly to the first polymer foam pad.

[0018] The anisotropic, thermally conductive layer can include boron nitride, graphite or graphene.

[0019] The energy storage system may also include a second thermal interface element comprising a second thermally conductive, thermosetting polymer foam pad disposed orthogonally to the first polymer foam pad between the heat sink and the energy storage cell stack. The second polymer foam pad is configured to couple the heat sink to the first polymer foam pad.

[0020] Each of the first polymer foam pad and the second polymer foam pad may have a matrix structure including a thermally conductive anisotropic and / or isotropic filler material, such as boron nitride, graphite, and graphene, and characterized by the foam density below 0.5 g / cm 3 is marked.

[0021] The second thermal interface element may be configured to couple the heat sink to the first thermal interface element and act as a thermal interface therebetween.

[0022] The energy storage system additionally includes a cold plate, such as a fin, extending adjacent to at least one of the first cell and the second cell. In such an embodiment, the second thermal interface element is configured to couple the heat sink to the cold plate and act as a thermal interface therebetween.

[0023] At least one of the first polymer foam pad and the second polymer foam pad is electrically conductive. The respective at least one of the first thermal interface element and the second thermal interface element additionally includes an electrically insulating layer configured to limit the loss of electrical energy from the energy storage cell pack.

[0024] The electrical insulating layer may be configured as a polyethylene terephthalate (PET) film.

[0025] The first polymer foam pad and / or the second polymer foam pad may be electrically non-conductive. In such an embodiment, at least one of the first polymer foam pad and the second polymer foam pad may be characterized by a lack of electrical insulation on the respective first polymer foam pad and the second polymer foam pad.

[0026] Yet another embodiment of the present disclosure is directed to a vehicle having an energy storage system according to the invention. The vehicle may employ a powerplant that uses electrical energy generated by such an energy storage system to generate torque.

[0027] The above features and advantages and other features and advantages of the present disclosure will be readily apparent from the following detailed description of the embodiment(s) and best mode(s) for carrying out the described disclosure, taken in conjunction with the accompanying drawings and the appended claims. Fig. 1 is a schematic diagram of a vehicle according to the disclosure employing a hybrid powertrain and an energy storage system configured to provide electrical energy thereto. Fig. 2 is a schematic close-up view of a cross-sectional top view of an embodiment of the energy storage system shown in Fig. 1, wherein the energy storage system includes a storage cell pack having a plurality of cells and thermal interface elements with thermally conductive, curable polymer foam cushions. Fig. 3 is a schematic perspective close-up view of a respective polymer foam cushion having a matrix structure. Fig. Figure 4A is a close-up view of a detailed view of a respective polymer foam cushion having an open-cell matrix structure. Fig. Figure 4B is a close-up view of a detailed view of a respective polymer foam cushion having a closed-cell matrix structure. Fig. 5 is a schematic close-up view of a cross-sectional top view of a specific embodiment of an electrically conductive heat-resistant matrix structure of a respective polymer foam cushion. Fig. 6 is a schematic close-up view of a cross-sectional top view of one embodiment of an electrically non-conductive heat-resistant matrix structure of a respective polymer foam cushion. Fig. 7 is a schematic close-up view of a cross-sectional top view of a specific thermal interface element having an anisotropic and / or isotropic thermal interface layer. Fig. Figure 8 is a schematic close-up view of a cross-sectional top view of another embodiment of the energy storage system shown in Fig. 1, which comprises a plurality of cells, thermal interface elements, and a cold plate extending adjacent to some of the cells.

[0028] With reference to the drawings, illustrated Fig. 1 depicts a vehicle 10. It should be understood that identical element symbols used on multiple figures refer to the same component or components of similar functionality. Additionally, the accompanying figures are intended merely to illustrate, not limit, the scope of the disclosure and should not be considered to scale. The vehicle 10 may be, but is not limited to, a commercial vehicle, an industrial vehicle, a passenger vehicle, a train, or the like. As shown, the vehicle 10 may be an electric or hybrid electric vehicle having one or more power sources or prime movers to provide vehicle propulsion.In particular, the vehicle 10 may include a first drive unit 12, such as an electric motor, and a second drive unit 14, such as an internal combustion engine, configured to generate respective drive torques for propelling the vehicle via wheels 16.

[0029] The vehicle 10 additionally includes an energy storage system 18 configured to provide electrical energy to each of the first drive unit 12 and the second drive unit 14 to enable the generation of the respective drive torques. As shown in Fig. 2, the energy storage system 18 includes a heat dissipation device, specifically, an energy storage cell pack 20, such as a battery pack. The energy storage cell pack 20 includes an adjacent first cell 20-1 and second cell 20-2. Each of the first and second cells 20-1, 20-2 is configured to generate and store electrical energy through electrochemical reactions that generate or release heat energy. Although the energy storage cell pack 20 is specifically shown as including first and second cells 20-1, 20-2, the energy storage cell pack may include various multiples of energy storage cells.

[0030] In the following description, the terms "energy storage cell," "battery," "cell," and "battery / accumulator cell" may be used interchangeably and refer to a variety of different cell chemistries and configurations, including, but not limited to, lithium-ion (e.g., lithium iron phosphate, lithium cobalt oxide, other lithium metal oxides, etc.), lithium-ion polymer, nickel-metal hydride, nickel-cadmium, nickel-hydrogen, nickel-zinc, silver-zinc, or other battery type or configuration. The term "battery / accumulator pack," as used herein, refers to multiple individual batteries contained within a single-piece or multi-piece housing, with the individual batteries electrically connected to achieve the desired voltage and capacity for a particular application.In addition, the storage cell pack 20 is illustrated schematically, and therefore not all battery / accumulator elements and / or battery / accumulator pack elements are shown in the illustrations.

[0031] The energy storage system 18 is configured to maintain uniform dissipation of the thermal energy emitted or released by the first cell 20-1 and the second cell 20-2 during the typically general charging and discharging of the cells. The energy storage system 18 is also intended to enable efficient dissipation of thermal energy under less common, e.g., abusive, operating conditions and to limit the possibility of thermal short circuiting in the energy storage cell pack 20. The energy storage system 18 is specifically configured to accomplish the above task via one or more lightweight, thermally conductive interfaces disposed between individual cells, e.g., 20-1, 20-2, and relative to adjacent structures, as discussed in detail below.

[0032] A variety of different abusive operating or charging conditions and / or manufacturing defects can cause a battery / accumulator, such as the one in battery / accumulator pack 20, to experience a thermal short circuit, where the amount of internally generated heat is greater than that which can be effectively dissipated. As a result, a large amount of thermal energy is rapidly released, heating the entire cell to a temperature of 900°C or more and causing the formation of local hot spots where temperatures can exceed 1500°C. Once a cell, such as cell 20-1, experiences a thermal short circuit, the thermal energy generated during that event can heat adjacent cells, such as cell 20-2, above their critical temperatures, thereby causing them to experience a thermal short circuit.These adjacent cells can, in turn, heat other cells to a temperature sufficient to cause them to thermally short circuit. Thus, the occurrence of a single cell experiencing a thermal short circuit can trigger a cascade reaction that can spread throughout the entire energy storage cell pack 20.

[0033] Although the description focuses on the energy storage system 18, other systems capable of rapidly releasing significant amounts of thermal energy are also considered within the scope of the present disclosure. Such systems may include, for example, consumer electronics such as telephones and personal computers, as well as other systems that include heat-releasing devices and that may utilize heat sinks to manage such thermal energy release. Accordingly, while the following description focuses on applications to the energy storage system 18 of the structures described below, applications to such other systems that utilize heat-dissipating devices are also contemplated.

[0034] With further reference to Fig. 2, the energy storage system 18 also includes a heat sink, such as a coolant plate or reservoir, configured to absorb and dissipate the thermal energy generated by the first and second cells 20-1, 20-2. The heat sink 22 may include a coolant loop 22-1 that utilizes coolant circulation tubes. The energy storage system 18 also includes a first thermal interface element 24 disposed between the first cell 20-1 and the second cell 20-2. The first thermal interface element 24 includes a first thermally conductive, curable polymer foam pad 26 (in Fig. 3 to 6). The foam pad 26 is constructed by blending a specific polymer with a suitable foaming agent, each of which is discussed in detail below. When so formed, the foam pad 26 material has a short working time, in the range of 1 to 5 minutes, and cures, i.e., it solidifies and assumes its final shape, within approximately 10 to 30 minutes after being injected or placed between the first and second cells 20-1, 20-2. Accordingly, the injected material, upon curing, forms a solid, strong, flexible, and long-lasting foam pad 26. During in-situ curing, the foam pad 26 is expected to exhibit substantially 0% shrinkage.As used herein, the term "solid" would refer to complete crosslinking of the liquid or gel to form a solid structure and would indicate a fully cured foamed material. In specific embodiments, the degree of curing is measured by sampling the material and testing it on a nuclear magnetic resonance machine to provide a degree of cure. Flowability may be determined before the material is crosslinked using a dynamic mechanical analyzer. As noted above, other systems capable of rapidly releasing significant amounts of thermal energy and utilizing a heat sink component, such as heat sink 22, are also contemplated.

[0035] As particularly in the Fig. 3 to 5, the first polymer foam pad 26 has a heat-resistant porous matrix structure 28. As shown in Fig. 3, the heat-resistant porous matrix structure 28 may include a conformable, lightweight base material 28A with thermally conductive, anisotropic and / or isotropic fillers 28B and voids or pores 28C. The cured, lightweight, porous matrix structure of the first polymer foam cushion 26 is configured to limit the spread of thermal energy between the first and second cells 20-1, 20-2 and to facilitate the transfer of waste heat from the storage cell pack 20 to the heat sink 22. In particular, the first polymer foam cushion 26 is configured to maintain direct, consistent, and uniform contact with the first cell 20-1 and the second cell 20-2 during alternate expansion of the cells 20-1, 20-2 as the cells are charged and contracted during discharge.In addition, the first polymer foam pad 26 is configured to absorb the thermal energy released by the first and second cells 20-1, 20-2 and conduct the thermal energy to the heat sink 22.

[0036] As discussed above, the base material 28A of the first polymer foam pad 26 forms the heat-resistant matrix 28 and is infused with thermally conductive, anisotropic, and / or isotropic fillers 28B. Generally, an "anisotropic" material has properties that are directionally dependent or differ in different directions, as opposed to an "isotropic" material, which has directionally independent properties. As specifically used herein, "anisotropic" refers to the material of the heat-resistant matrix 28 having thermal conductivity that is directionally dependent, i.e., unequal when measured along different axes. The difference in the physical or mechanical properties of a material, e.g., the thermal conductivity of the first polymer foam pad 26, can be identified when measured along different X and Y axes.In the case of the first polymer foam pad 26, the anisotropic properties of the material can be used to advantageously determine the direction of the thermal conductivity of that pad. For example, for the most efficient dissipation of thermal energy from the storage cell pack 20 to the heat sink 22 via the first thermal interface element 24, the thermal conductivity of the first polymer foam pad 26 in the XY plane along the Y-axis may be greater than the thermal conductivity along the X-axis (in . Fig. 5 shown).

[0037] The base materials 28A of the matrix 28 can be selected from a list of heat-resistant, thermosetting polymers including, but not limited to, silicone, acrylic, polyurethane, polyvinyl esters, polycycloolefins (e.g., polyoctenamers such as Vestenamer 8012 or 6213), polyolefins (e.g., polybutadienes, poly(1-olefins)), and polystyrene. The fillers can be selected from a list of anisotropic materials including, but not limited to, boron nitride, graphite, and graphene, and / or from a list of isotropic fillers including, but not limited to, aluminum nitride, silicon carbide, aluminum oxide, zinc oxide, metallic powders, synthetic diamond, or mixtures thereof. Each of the contemplated fillers is thermally conductive, either by itself or as admixtures thereof.Any of the base materials 28A can be used to form the basic structure of the polymer foam cushion 26 with the addition of the aforementioned foaming agent. The foaming agent can be an inert gas, such as nitrogen, argon, or air.

[0038] The required thermal conductivity of the foam pad 26 can be achieved either via an open-cell foam structure 28-1 (in Fig. 4A) or a closed-cell foam structure 28-2 (in Fig. 4B) of the matrix 28. The foaming agent can be introduced as hollow microcapsules into the closed-cell foam structure 28-2 of the matrix 28. Such hollow microcapsules can be either pre-expanded or mixed as heat-activated expanding microcapsules with the filler material and with the heat-resistant polymers. The microcapsules can be formed, for example, from polyvinylidene chloride-polyacrylonitrile. The microcapsules can be used in either expanded or unexpanded form. Depending on the foaming agent, expanded microcapsules can come in different size dimensions or diameters, for example, 33-55, 30-50, 55-85, or 30-50 micrometers. Similarly, various unexpanded foaming agent microcapsules can also come in different size dimensions, for example, 10-16, 9-15, 18-24, or 28-38 micrometers.Unexpanded microcapsules can be activated to expand at temperatures of approximately 80 to 190 degrees Celsius, depending on the foaming agent.

[0039] The first polymer foam pad 26 may have a foam material density below 0.5 g / cm 3 and further below 0.3 g / cm 3 . In particular, the first polymer foam pad 26 may have a material density in the range of 0.1 to 0.2 g / cm 3 whereby the lightweight structure of the first thermal interface element 24 (in Fig. 7). With respect to the exemplary matrix base materials 28A, silicones are typically polymers that include an inert, synthetic compound composed of repeating units of siloxane, which is a chain of alternating silicone atoms and oxygen atoms combined with carbon, hydrogen, and sometimes other elements. Expanding foam-forming silicones are typically heat-resistant and electrically non-conductive. In particular, expanded graphite interferes with the foaming of a two-part silicone, such as Elastocil. Accordingly, in such an embodiment, microcapsules may be used to construct a closed-cell foam cushion 26.

[0040] Acrylic elastomers belong to a group of polymers commonly referred to as plastics. Acrylic elastomers are characterized by their transparency, fracture strength, and elasticity. Acrylic elastomers exhibit properties of heat and chemical resistance.

[0041] In general, polyurethane is a polymer composed of organic units linked by carbamate (urethane) bonds. While most polyurethanes are thermosetting polymers that are heat-stable, meaning they do not melt when heated, thermoplastic polyurethanes are also available.

[0042] Typically, polyvinyl esters, or vinyl polymers, are a group of polymers derived from vinyl monomers. An ester is a chemical compound derived from an organic or inorganic acid. Esters are generally derived from a carboxylic acid and an alcohol. Polyvinyl esters are often thermally stable and electrically non-conductive.

[0043] Polystyrene is generally a synthetic aromatic hydrocarbon polymer made from the monomer styrene. Polystyrene can be solid or expanded and is electrically non-conductive.

[0044] In general, boron nitride is a heat- and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. Boron nitride exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The cubic (sphalerite structure) variety, analogous to diamond, is called c-BN; it is softer than diamond, but its thermal and chemical stability is greater.

[0045] In general, graphite is a crystalline allotrope of carbon, a metalloid, a native element mineral, and a form of coal. Graphite is the most stable form of carbon under standard conditions. Graphite has a layered, planar structure. The individual layers are called graphene. In each layer, the carbon atoms are arranged in a honeycomb lattice. Atoms in the plane are covalently bonded, with only three of the four potential bonding sites being filled. The fourth electron is free to migrate in the plane, making graphite electrically conductive. However, graphite does not conduct electricity in a direction perpendicular to the plane. Other forms of carbon can also be used as functional thermally conductive materials, including carbon nanofibers and nanotubes.

[0046] As in Fig. 7, the first thermal interface element 24 may also include an anisotropic and / or isotropic, thermally conductive layer 30 disposed between the first polymer foam pad 26 and at least one of the first cell 20-1 and the second cell 20-2. The layer 30 is configured to conduct the thermal energy released by the first cell 20-1 and / or the second cell 20-2 to the heat sink 22 (in Fig. 2 and Fig. 7). The layer 30 may be a coating or a film applied directly to the first polymer foam pad 26. The layer 30 may include or be formulated from anisotropic and / or isotropic thermally conductive materials including, but not limited to, boron nitride, graphite and graphene, aluminum nitride, silicon carbide, aluminum oxide, zinc oxide, metal powder, synthetic diamond, or mixtures thereof. Such an embodiment of the first thermal interface element 24 may be used as the primary heat transfer medium disposed between the first cell 20-1 and the second cell 20-2.

[0047] With reference to Fig. 8, the energy storage system 18 may also include a cold plate or fin 32 extending along and adjacent to at least one of the first cell 20-1 and the second cell 20-2 as a further heat transfer medium. As in Fig. 8, in an energy storage cell pack 20 that is larger than the two present cells 20-1, 20-2, cold plates 32 can be positioned between the respective cell pairs, thus alternating with the first thermal interface elements 24 in such a cell pack. In such an embodiment, each cell 20-1, 20-2 will be in contact with a first thermal interface element 24 and a cold plate 32. With reference to each of the Fig. 2 and Fig. 7, the energy storage system 18 may additionally include a second thermal interface element 34. The second thermal interface element 34 is configured to enclose a second thermally conductive, curable polymer foam pad 36.

[0048] As shown, the second polymer foam pad 36 is disposed orthogonally to the first polymer foam pad 26 between the heat sink 22 and the energy storage cell stack 20. The second polymer foam pad 36 is configured to couple the heat sink 22 to the first polymer foam pad 26 and operate as a thermal interface therebetween. In the embodiment of the energy storage system 18 including a cold plate 32, the cold plate is in direct contact with the second polymer foam pad 36. As such, the second thermal interface element 34 may be additionally configured to couple the heat sink 22 to the cold plate 32 and operate as a thermal interface therebetween.

[0049] Similar to the first polymer foam pad 26, the second polymer foam pad 36 may be constructed as a heat-resistant matrix 28 of a deformable, lightweight base material 28A with thermally conductive, anisotropic and / or isotropic, thermally conductive fillers 28B, as described in the Fig. 3 and Fig. 4. Anisotropic and / or isotropic, thermally conductive material properties of the second polymer foam pad 36 (in Fig. 8) can be used to advantageously establish the direction of thermal conductivity of the second pad for the most effective dissipation of thermal energy from the first thermal interface element 24 to the heat sink 22 via the second thermal interface element 34. Similar to the first polymer foam pad 26, the second polymer foam pad 36 (in Fig. 8) a foam density below 0.5 g / cm 3In particular, the material density of the second polymer foam pad 36 can be in the range of 0.1 to 0.2 g / cm 3 which enables the lightweight structure of the second thermal interface element 34.

[0050] The heat-resistant matrix 28 of each of the first polymer foam pad 26 and the second polymer foam pad 36 may be electrically conductive. In the embodiment of the electrically conductive first polymer foam pad 26, it is additionally provided that the first thermal interface element 24 comprises an electrical insulating layer (38) or an electrical element (in Fig. 5). The electrical insulation layer 38 is configured to limit the loss of electrical energy from the energy storage cell pack 20 to the environment through the first polymer foam cushion 26. As shown, one example of the electrical insulation layer 38 may be disposed between the first polymer foam cushion 26 and the first cell 20-1, and another example of the electrical insulation layer 38 may be disposed between the first polymer foam cushion and the second cell 20-2.

[0051] In the embodiment of the electrically conductive second polymer foam pad 36 used in the Fig. 2 and Fig. 7, the second thermal interface element additionally includes an electrical insulating layer 40. Similar to the electrical insulating layer 38 shown in Fig. 5, the electrical insulating layer 40 is configured to limit the loss of electrical energy from the energy storage cell pack 20 to the environment. In particular, the electrical insulating layer 40 is configured to limit the loss of electrical energy from the energy storage cell pack 20 through the second polymer foam cushion 36. As shown, the electrical insulating layer 38 may be disposed between the second polymer foam cushion 36 and the first cell 20-1, and another example of the electrical insulating layer 38 may be disposed between the first polymer foam cushion 26 and the heat sink 22. Each of the electrical insulating layers 38, 40 may be configured, for example, as a polyethylene terephthalate (PET) film.

[0052] Alternatively, each of the first polymer foam cushions 26, as shown in Fig. 6, and the analogous second polymer foam pad 36 (not shown). In the embodiments of the electrically conductive first and second polymer foam pads 26, 36, each of the present polymer foam pads is characterized by the absence of an electrical insulating element, such as the insulating layer 40 shown in the Fig. 2 and Fig. 7. In other words, an electrically non-conductive first polymer foam pad 26 (and the analogous second polymer foam pad 36) does not require electrical insulation to limit loss of electrical energy from the energy storage cell pack 20 to the environment.

[0053] In general, either one or both of the first and second thermal interface elements 24, 34 may be used in the energy storage system 18, whether for powering the vehicle 10 or for power generation in another device. Additionally, one or both of the first and second thermal interface elements 24, 34 may be used to remove, i.e., capture and redirect, unused thermal energy emitted by various heat-emitting devices. With respect to the present disclosure, heat-emitting devices that emit thermal energy as a byproduct of their primary operation may be present in assemblies such as control modules, electric motors, computers, and other high-resistance electrical and electronic applications.

Claims

[1] Energy storage system (18) comprising: a heat dissipation device, in particular an energy storage cell pack (20) including a first cell (20-1) and a second cell (20-2) arranged adjacent to the first cell (20-1), each of the first and second cells (20-1, 20-2) being configured to generate and store electrical energy through electrochemical reactions that generate heat energy; a heat sink (22) configured to absorb and dissipate the thermal energy released by the first and second cells (20-1, 20-2); and a first thermal interface element (24) disposed between the first cell and the second cell (20-1, 20-2), comprising a first thermally conductive, curable polymer foam pad (26) and configured to: maintain uniform contact with the first cell and the second cell (20-1, 20-2) during alternating expansion of the first and second cells (20-1, 20-2) during charging and contraction of the first and second cells (20-1, 20-2) during discharging; and absorb the heat energy released by a heat dissipation device formed by the first cell (20-1) and the second cell (20-2) and conduct the heat energy to the heat sink (22), wherein a further thermal interface element (34) arranged between the heat sink (22) and the heat dissipation device and comprising: a thermally conductive, curable further polymer foam pad (36) configured to maintain uniform contact with each of the heat sink (22) and the heat dissipator, absorb thermal energy released by the heat dissipator, and conduct the released thermal energy to the heat sink (22); characterized by , that the further polymer foam pad (36) has a matrix structure (28) which includes at least one of an anisotropic thermally conductive filler material and an isotropic thermally conductive filler material and is characterized by a foam density below 0.5 g / cm 3 is marked, and that the further polymer foam pad (36) is electrically conductive and the further thermal interface element (34) additionally includes an electrical insulating layer (40) or the further polymer foam pad (36) is electrically non-conductive and is characterized by the absence of an electrical insulating element. [2] The energy storage system (18) of claim 1, wherein the further thermal interface element (34) further comprises a thermally conductive layer (30) configured to conduct the thermal energy released by the heat dissipation device to the heat sink (22). [3] The energy storage system (18) of claim 2, wherein the thermally conductive layer (30) is anisotropic and includes at least one of boron nitride, graphite, and graphene. [4] The energy storage system (18) of claim 2, wherein the thermally conductive layer (30) is isotropic and includes at least one of aluminum nitride, silicon carbide, aluminum oxide, zinc oxide, metal powders, and synthetic diamond. [5] The energy storage system (18) of claim 1, wherein the further polymer foam cushion (36) includes a heat-resistant, thermosetting polymer comprising at least one of silicone, acrylic, polyurethane, polyvinyl ester, polycycloolefin, polyolefin, and polystyrene. [6] Energy storage system (18) according to claim 1, wherein: the matrix structure (28) comprises one of an open-cell and a closed-cell foam structure (28-1, 28-2); and the closed-cell foam structure (28-2) encloses foaming agent microcapsules. [7] The energy storage system (18) of claim 1, wherein the electrical insulating layer (40) is configured as a polyethylene terephthalate (PET) film. [8] Vehicle (10), characterized by an energy storage system (18) according to at least one of claims 1 to 7.

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